It looks like those will only replace a 7440/single filament bulb. We have dual filament 7443's in the front, which is probably why we're having so much trouble with them.No Hyper Flash 7440 LED Turn Signal Light Bulbs, Plug-N-Play Style
Sent from the wrong side of the tracks.
FYI I have also tried these without success. Just in case you go down that road.Actually ended up getting in touch with DD about the lights. Their theory is similar to my dad's: not enough resistance on that circuit, so they suggested another resistor in parallel. Going to try that soon and see what happens. Nice link on the JDMToy stuff, by the way. Might have to try it if this doesn't work.